1. Field of the Invention
The present invention relates to mesoporous structures.
2. Description of the Prior Art
The International Union of Pure and Applied Chemistry, IUPAC, classifies porosity on the basis of pore diameter, d.sub.p. Mesoporous materials are defined by IUPAC as those materials in which 2 nm mesoporous inorganic materials comprise inorganic xerogels (e.g., the common silica desiccants), pillared clays, and the subject matter of this patent viz. mesoporous molecular sieves (MMS), discovered by researchers at Mobil and are described U.S. Pat. No. 5,098,684, issued to Kresge et al. On Mar. 24, 1992 and U.S. Pat. No. 5,057,296 issued to J. S. Beck on Oct. 15, 1991, the entire contents and disclosures of which are hereby incorporated by reference. These materials are referred to in the literature as the MCM (Mobil composition of matter) family of materials. MMS prepared generally as powders have received enormous attention by the research community since their announcement by Kresge et al. (Kresge C. T., Leonowicz M. E., Roth W. J., Vartuli J. C., Beck J. S., Nature, 1992, 359: 710-712). In the past two years, advances have been made in understanding and exploiting the supramolecular templating process used in MMS formation, development of new synthetic procedures, extending the compositional range beyond silicas, and processing of MMS as thin films. MMS are high surface area amorphous solids (surface area up to 1400 m.sup.2/g) characterized by monosized cylindrical pores, ranging from about 12-100 .ANG. in diameter, organized into periodic arrays that often mimic the liquid crystalline phases exhibited by surfactants. MMS synthesis procedures typically require four reagents: water, surfactant, a soluble inorganic precursor, and catalyst. MMS form (as precipitates) in seconds to days (Beck J. S., Vartuli J. C., Roth W. J., Leonowicz M. E. Kresge C. T., Schmitt K. D., Chu C. T. W., Olson D. H., Sheppard E. W., McCullen S. B. et al., J. Am. Chem. Soc., 1992, 114: 10835; Huo Q., Margolese D. L., Ciesla U., Demuth D. G., Feng P., Gier T. E., Sieger P., Firouzi A., Chmelka B. F., Schuth F., Stucky G. D., Chem. Mater., 1994, 6: 1176-1191) at temperatures ranging from 180. degree. C. to as low as xe2x88x9214. degree. C., depending on the inorganic precursor. Before pyrolysis or surfactant extraction, pure silica MMS exhibit three structure types: (1) hexagonal (referred to as H or MCM-41), a 1-d system of hexagonally ordered cylindrical silica channels encasing cylindrical surfactant micellar assemblies; (2) cubic (C), a 3-d, bicontinuous system of silica and surfactant; and (3) lamellar, a 2-d system of silica sheets interleaved by surfactant bilayers.
Over the past several years various MMS synthetic pathways have been elucidated (Beck J. S., Vartuli J. C., Curr. Opinion in Solid State and Material Science, 1996, 1: 76-87). Experimentally, it has been shown that MCM-41 type phases form under conditions in which the surfactantxe2x80x94before the addition of the silica sourcexe2x80x94is: a) free (surfactant concentration, c, is less than the critical micelle concentration for spherical micelles, c. In the past several years, there has been synthesized multicomponent and non-silica MMS (Huo Q., Margolese D. L., Ciesla U., Demuth D. G., Feng P., Gier T. E., Sieger P., Firouzi A., Chmelka B. F., Schuth F., Stucky G. D., Chem. Mater., 1994, 6: 1176-1191) for catalytic applications due to their higher surface areas and greater accessibility of active sites compared to zeolites.
In the past few years various pathways have been explored to access a wide spectrum of mesostructured materials with tunable pore sizes and arrangements (orientation) and good compositional control. These materials include ionic, covalent and electrostatic interactions, and they permit the addition of salts and auxiliary solvents. A variety of macro- and microstructures have been synthesized such as powders, fibers, monoliths, thin films, hollow and transparent hard spheres, and aerosol particles, which find applications in catalysis, membrane separation, sensors, optoelectronics and as novel nanomaterials, see Jackie Y. Ying, C. P. Mehnert, M. S. Wong Angew. Chem. Int. Ed. 1999, 38, 56-77.; C. J. Brinker Curr. Opin. Solid State Mater. Sci., 1, 798-805, 1996; J. C. Vartuli, C. T. Kresge, W. J. Roth, S. B. McCullen, J. S. Beck, K. D. Schmitt, M. E. Leonowitz, J. D. Lutner, E. W. Sheppard in Advanced Catalysts and Nanostructured Materials: Modem Synthesis Methods (Ed: W. R. Moser) Academic Press, N.Y., 1-19(1996); G. D. Stucky, Q. Huo, A. Firouzi, B. F. Chmelka, S. Schacht, I. G. Voigt Martin, F., Schxc3xcth in Progress in Zeolite and Microporous Materials, Studies in Surface Science and Catalysis, 105, (Eds: H. Chon, S. K. Ihm, Y. S. Uh), Elsevier, Amsterdam, 3-28, (1997); N. K. Raman, M. T. Anderson, C. J. Brinker Chem. Mater., 8, 1682-1701. 1996; D. M. Antonelli, J. Y. Ying, Curr. Opin. Coll. Interf. Sci., 1, 523-529, 1996.; D. Zhao, P. Yang, Q. Huo, B. F. Chmelka and G. D. Stucky, Current Opinion in Solid State and Materials Science, 3,111-121, 1998; Y. Lu, H. Fan, A. Stump, T. L. Ward, T. Rieker, C. J. Brinker, Nature, 398, 223-226, 1999. However, none of these process has provided the ability to design these materials with a controlled combination of mesophases or the ability to pattern functionality.
It is therefore an object of the present invention to provide a lithographic process which allows control of structure and properties (refractive index, thickness, porosity, pore orientation) and functionality of meso-ordered films, powders and bulk systems.
It is another object of the present invention to provide a lithographic process that uses the presence of a photoactive/photosensitive species to affect the mesophase of meso-ordered films, powders and bulk systems.
It is yet another object of the present invention to provide a lithographic process that uses a photoactive/photoresponsive amphiphile to affect the mesophase of meso-ordered films, powders and bulk systems.
It is yet another object of the present invention to provide a lithographic process that uses photoacid/base generation to affect the mesophase of meso-ordered films, powders and bulk systems.
It is yet another object of the present invention to provide a lithographic process that uses photoacid/base generation to affect the sol-gel network of meso-ordered films, powders and bulk systems.
It is yet another object of the present invention to provide a lithographic process that incorporates a photoacid/base generator in mesopores to obtain better resolution of pattern transfer and hence etching of sol-gel network in meso-ordered films, powders and bulk systems.
It is yet another object of the present invention to provide a lithographic process that induces temporary hydrophobicity in controlled regions via the use of a photoactive species.in meso-ordered films, powders and bulk systems.
It is yet another object of the present invention to provide a lithographic process that uses photolysis to carry out polymerization along with mesophase changes to get hybrid materials in meso-ordered films, powders and bulk systems.
It is yet another object of the present invention to provide a lithographic process that allows acid-base sensitive chemistry to be performed in mesostructured thin films.
It is yet another object of the present invention to provide a lithographic process that allows functionalized materials to be obtained.
It is yet another object of the present invention to provide a lithographic process that is suitable for compounds of Si, Al, B, Pb, Sn, Ti, Zn, Zr, Ce, La, Y and Nd which are capable of sol-gel processing.
According to a first broad aspect of the present invention, there is provided a mesoporous material comprising at least one region of mesoporous material patterned at a lithographic scale.
According to a second broad aspect of the invention, there is provided a method for forming a patterned mesoporous material comprising: coating a sol on a substrate to form a film, the sol comprising: a templating molecule, a photoactivator generator, a material capable of being sol-gel processed, water, and a solvent; and exposing the film to light to form a patterned mesoporous material.
Other objects and features of the present invention will be apparent from the following detailed description of the preferred embodiment.